Moon Lake Dam

Moon Lake Dam is a zoned earthfill, rockfaced dam built just downstream from a naturally occurring lake known as Moon Lake. The original lake has an estimated capacity of 13,900 acrefeet. The dam has a structural height of 98 feet and a volume of 513,000 cubic yards. Moon Lake Reservoir, on the West Fork of the Lake Fork of the Duchesne River, has a total capacity of 35,800 acre feet. The combined total of the original lake plus constructed storage is 49,500 acre feet. The surface area of the lake is 770 acres at 8137 feet elevation. Construction of Moon Lake Dam started in 1935 and finished in 1938. Curb and parapet were added in 1940 and finished in 1941.

Geology

Moon Lake Project lies partly on the south flank of the Unita Mountain Range and partly on the north limb of the Unita Basin in northeastern Utah. The Unitas are the southeastern range of the central Rocky Mountains while the Unita Basin is the northern feature of the Colorado Plateau province. The Unita Mountains are a highly eroded, east-west trending anticline whose crest has been raised by a series of block faults. The core of the range is composed of Precambrian rock that has been exposed by deep erosion. The Unita Basin is a very deep structural trough that has been filled with Tertiary and Recent age sediments. There is perhaps as much as 30,000 feet of displacement between the elevation of a bed in the crest of the range and on the axis of the basin.